Counting circuit



Aug. 25, 1959 A. G. THOMAS COUNTING CIRCUIT Filed Sept. 19. 1957 WW INVENTOR.

United States Patent i J ce COUNTING CIRCUIT Albert G. Thomas, Charlottesville, Va., assignor to Industrial Controis Corporation, Chattanooga, Tenn., a corporation of Tennessee Application September 19, 1957, Serial No. 684,969

16 Claims. (Cl. 315-845) This invention relates to counting circuits, generally, and especially to counting circuits for controlling step motors similar to those described in my US. Patent Number 2,774,922.

In prior counting circuits it has often been difiicult to adjust the grid biases and other factors so that reliable operation could be obtained. Usually there had to be a rather delicate balance between the bias potentials and the applied pulse voltages since, if the pulses were of too high value, all tubes in the counting circuit would be fired and if the potential of the pulses was too low the tubes would not be fired in sequence. The delicacy of adjustment necessary made these prior counting circuits of doubtful value in many instances, especially since the characteristics of tubes and associated circuit components often changed with variation of temperature or current.

In order to overcome the above and other objections to prior counting circuits, I have devised an improved counting circuit of relatively great stability and reliability of operation.

' An object is to provide a counting circuit of relatively simple construction for use in computers, counters, motor control circuits, and for other applications.

Another object is to provide a reliable counting circuit which can be pulsed with relatively strong signals or relatively high voltages without blocking the operation of the circuit by firing more than one tube at a time, or otherwise causing the circuit to operate improperly.

A further object is to provide a counting circuit which will effectively accept operating pulses of relatively wide range of voltage or current strength. 7

An additional object is to provide a counting circuit of reliable operation and which does not have to be frequently adjusted.

Another object is to provide a counting circuit which can be pulsed at relatively high rates.

Other objects will be evident in the following description,

In the drawings:

Figure 1 is a circuit diagram of my improved counting circuit for one sequence of energization of the thyratrons or other current control devices.

Figure 2 is a partial circuit diagram similar to that of Figure l and including like components similarly numbered. This circuit has relay means for reversing the order of energization of the thyratrons or other current control devices.

In Figure 1 thyratron 1 is connected in series with the first phase motor winding 4 and resistor 5 in the anode circuit and in series with resistor 6 in the cathode circuit between positive line 7 and negative line 8 which lines are connected, respectively, with the positive and negative terminals of a source of direct current such as a generator, rectifier, or the equivalent. The motor winding 9 of the second phase is connected in series with resistor 10 which is connected to the anode of thyratron 2', the cathode of which is connected to one end of resistor 11, the other'end of which is connected to negative line 8. Similarly, the motor winding. 12 of the third phase is connected in series with resistor 13 between positive 2,901,668 Patented Aug. 25, 1959 line 7 and the anode of thyratron 3. Resistor 14 is connected between the cathode of thyratron 3 and negative line 8. Condenser 15 is connected between the anodes. of thyratrons 1 and 2; condenser 16 is connected between the anodes of thyratrons 2 and 3;, and condenser 17 is connected between the anodes of thyratrons 1 and 3. These condensers and resistors 5, 10, and 13 serve to cause any fired thyratron to be extinguished when any of the other three thyratrons is fired. The values of these condensers and resistors can be widely varied, depending. upon the type of thyratron used, load conditions, and.

other factors. As a typical example fora motor whose windings carry 3 amperes for each phase, the condensers may have a capacitance of 10 to 3'0 mfd. and the resistors 5, 10, and 13 maybe of 20' to 40 ohms each, assuming a. voltage between lines 7 and 8 of 200 to 250 volts. These values are given merely to give a general idea rather than. as limiting values.

The windings 4, 9, and 12 may be either stator or rotor windings, or both. These windings may be arranged as described in my US. Patent Number 2,774,922 or in any suitable manner. That patent also describes my step motor. The cathodes of the thyratrons are connected with suitable transformers or other sources of current. While thyratrons are shown, it is contemplated that transistors, magnetic amplifiers, or the equivalent, can be used.

The negative terminal of bias battery 18 is connected to the grid of thyratron 1 and the positive terminal of this battery is connected to one end of resistor 19, the

other end of which is connected to negative line 8. Battery l8 normally biases-thyratron 1 sutficiently negatively to prevent firing thereof. Battery 20 and resistor 21 are similarly connected between the grid of thyratron 2 and negative line 8 to prevent firing of thyratron 2, normally.

factors. In the specific case cited above, the bias units may apply negative potentials of to volts to'the thyratron grids but, again these are not limiting values.

Primary winding 24 of preferably pulse type trans former T is connected between the anode of avacuated tube 25 and conductor 29. The cathode of tube 25 is connected to negative line 8. This tube is shown as a triode but may be a tetrode or pentode type with low internal capacitance to prevent passage of pulses therethrough when properly biased. The positive terminal of battery or other bias source 26 is connected to the cath-' ode of thyratron 1 and the negative terminal of bias source 26 is connected to the control grid of tube 25 which is preferably normally biased negatively to the point of cutoff. Hard tubes 27 and 28 are similar to tube 25 and have their anodes connected to conductor 29 through respective primary windings 30 and 31 of transformers T and T low internal capacitance and may be tetrodes or pentodes. The transformers T and T are similar to transformer T and have respective secondary windings 32 and 33. The winding 32 is connected between the positive termi nal of bias battery 22 and to line 8; and winding 33 is connected by conductor 34 to the positive terminal of bias battery 18, and to line 8. The tubes 27 and 28, like and negative line 8.

Pulsing device 35 is provided. This may be an oscillator, commutator, or any source of pulses of sufiicient The negative bias required will depend upon the thyratrons used, voltages, and other These tubes should also have amplitude to cause firing of the thyratrons. This pulser preferably provides direct current pulses which may be indirectly applied intermittently to the respective resistors 19, 21, and 23 in sequence to overcome the negative bias potentials of the thyratrons and so to cause firing thereof. It is preferable that'the positive pulses applied to the thyratron grids be greater than the negative bias potentials by a sufficient margin to insure firing of the thyratrons. In practice a positive potential excess of volts or more is usually sufficient for this purpose.

The value of resistors 19, 21, and 23 is chosen with respect to the voltage of the pulses and the grid currents of the thyratrons, and other factors such as transformer ratio, 'so that the induced current flow through these resistors as a result of application of sequential pulses, will develop the required positive firing potentials on the thyratron grids. While considerable latitude is possible, as a practical example, these resistors may be of 10,000 to 25,000 ohms for thyratrons passing currents of about 3 to 6 amperes.

In operation, the positive and negative lines 7 and 8 are connected to a suitable source of direct current power and the cathodes of the thyratrons and hard tubes are suitably energized. Then any thyratron may be fired by connecting the grid to the cathode or in other manner. It will be assumed that thyratron 1 is fired. Current flow through resistor 6 then develops a positive potential on the grid of tube 25 sufficient to overcome the negative bias of battery 26 and so tube 25 will become conductive. Resistors 6, 11, and 14 are chosen of such value that positive potentials sufiicient to overcome the negative biases of batteries 26, 37, and 38 connected between the respective cathodes of thyratrons 1, 2, and 3 and the grids of tubes 25, 27, and 28 are developed by current flow through these resistors. Normally tubes 25, 27, and 28 are biased negatively to the point of cut-ofi by batteries 26, 37 and 38.

Now, thyratron 1 has been fired and tube 25 has become conductive. Therefore when the next positive pulse is applied to conductor 29 by unit 35 a pulse of current will pass through transformer winding 24 and tube 25 but virtually no current will pass through windings 30 and 31 and tubes 27 and 28 since these tubes are negatively biased. The pulse of current through primary winding 24 will induce a current pulse in secondary winding 36 and the phasing is such that the induced current will flow through resistor 21 in the direction of the arrow to produce a positive potential on the grid of thyratron 2 of sufficient voltage to overcome the negative bias of battery and so to fire thyratron 2. When this occurs, thyratron 1 is quickly extinguished through the agency of condenser 15 and associated circuitry. The extinction of current in tube 1 causes negative bias battery 26 to bias tube to the point of cut-off and so now the only conductive hard tube is tube 27. When the next positive pulse is applied to conductor 29 a current pulse in transformer Winding 30 and tube 27 occurs and a properly phased positive pulse is induced in secondary winding 32 to cause firing of thyratron 3 in the same manner in which thyratron 2 was fired; the thyratron 2 being extinguished through the agency of condenser 16. Again the extinction of thyratron 2 causes tube 27 to become non-conductive so that now hard tube 28 only is conductive as a result of current flow through resistor 14. The next positive current pulse applied to conductor 29 passes through primary winding 31 and tube 28 and induces a properly phased current pulse in secondary winding 33 which, in the same manner previously described, causes thyratron 1 to be fired again, which through condenser 17, causes thyratron 3 and tube 28 to become non-conductive. The ring circuit or counting circuit described will continue to cause firing of the thyratrons in the sequence described as long as intermittent positive pulses of proper amplitude are applied between positive conductor 29 and negative line 8.

Each time a thyratron is fired the associated motor winding 4, 9, or 12, is energized so that the motor will rotate in steps as described in Patent Number 2,774,922. A suitable brake for the motor can be provided. It is obvious that this circuit, or the equivalent, may likewise be used for various counting operations as in computers and for other purposes. A marked advantage of this circuit over prior counting circuits is that, in effect, each thyratron is virtually isolated until its turn to fire comes and then that is the only thyratron which will receive a firing pulse. This provides great reliability of operation as compared to prior counting circuits which had to be closely adjusted and which often allowed all three thyratrons to fire, especially under changing temperature or other conditions which may alter the values or characteristics of components. In my circuit a wide bias voltage variation may occur without impairment of positiveness of operation. While three thyratrons are shown, the circuit may include any desired number of thyratrons or other current control elements such as a decade, for instance, for computer operation. Another advantage of my circuit is that the pulses may be relatively long Without firing but one tube at a time.

In Figure 2, means for causing reversal of the order of firing the thyratrons is included. The positive line and elements 4, 9, 12, 5, 10, 13, 15, 16 and 17 are not shown but are connected similarly as in Figure 1. In

this case one terminal of each of the secondary windings 36, 32, and 33 is connected, respectively, to single pole double throw relay arms or armatures 39, 40 and 41. The other terminals of these secondary windings are connected to the cathodes of tubes 25, 27, and 28 and so to negative line 8. Normally closed contacts 42, 43, and 44 associated with respective relay arms 39, 40, and 41 are connected, respectively, with the positive terminals of bias batteries 18, 20 and 22, as indicated. Normally open contacts 45, 46 and 47, associated with respective relay arms 39, 40 and 41, are connected, respectively, with the positive terminals or poles of bias batteries 20, 22 and 18, as shown. Relay coil or winding 48 may be suitably energized when it is desired to reverse the order of firing the thyratrons so that all three relay arms 39, 40 and 41 are pulled over against the respective contacts 45, 46 and 47. The relay arms are indicated as mechanically connected but they are, of course, insulated each from the other.

For normal or forward operation of the motor the windings 4, 9, and 12 are energized in that order, the relay arms being in the positions shown in Figure 2. When it is desired to reverse the direction of rotation of the motor the relay magnetizing winding 48 is energized with the result that relay arms 39, 40, and 41 are moved over against respective contacts 45, 46, and 47, thus reversing the order of firing the thyratrons as pulses are applied to the circuit through conductor 29 and negative line 8. When coil or winding 48 is deenerized, the relay arms are moved back to the positions shown, by the relay spring. This ability to reverse the order of energizing the tubes 1, 2, and 3, or other current control devices, may be used to efiect subtraction or division in computers, the forward or normal order of energization being used for addition or multiplication. There are other uses for the reversible counting circuit.

Numerous variations of details of construction are possible without departing from the general principles which I have disclosed. For instance, the firing pulses in the transformers may be developed as a result of reduction of current in the auxiliary hard tubes rather than by an increase of current and other coupling means than transformers may be used. It has already been stated that transistors, magnetic amplifiers, or other current control devices may be used in place of thyratrons.

What I claim is:

1. In a counting circuit, a plurality of principal gridcontrolled current control devices, a plurality of auxiliary grid-controlled current control devices associated therewith, means conductively connecting said principal current control devices and said auxiliary current control devices to affect the electrical conductivity thereof as a result of steady current flow in said principal current control devices, means electrically connecting said auxiliary current control devices with said principal current con trol devices to affect the electrical conductivity thereof as a result of pulsed current flow in said auxiliary current control devices, and means for producing intermittent current flow in said auxiliary current control devices.

2. The counting circuit as described in claim 1, said means for producing current fiow in said auxiliary current control devices comprising pulsing means simultaneously applied to said auxiliary current control devices.

3. The counting circuit as described in claim 1, said first named current control devices having control elements, and including means electrically connected with said control elements for causing reversal of the sequence of current flow in said principal current control devices.

4. In a counting circuit, a plurality of principal current control devices, a plurality of auxiliary grid-controlled current control devices associated therewith, means electrically connecting said principal current control devices and said auxiliary current control devices to affect the electrical conductivity thereof as a result of steady current flow in said principal current control devices, transformer means electrically connecting said auxiliary current control devices with said principal current control devices to effect the electrical conductivity thereof as a result of pulsed current flow in said auxiliary current con trol devices, and means for applying intermittent currents to said auxiliary current control devices.

5. In a counting circuit, a plurality of principal current control devices, a plurality of other grid controlled current control devices associated therewith, means connecting said principal current control devices and said other current control devices to cause increased effective electrical conductivity thereof as a result of steady current flow through said principal current control devices, transformer means electrically connecting said other current control devices and said principal current control devices to cause increased effective electrical conductivity thereof as a result of pulsed current flow through said other current control devices, and means for applying intermittent electrical energy to said other current control devices and said transformer means.

6. In a counting circuit, a plurality of principal gaseous current control devices having control elements therefor, means normally biasing said control elements to prevent substantial flow of current through said principal current control devices, a plurality of evacuated current control devices having control members therefor, means normally biasing said control members to prevent substantial flow of current through said evacuated current control devices, means connecting said principal current control devices with said control members to make possible increased flow of current through said other current control devices as a result of steady flow of current through said principal current control devices, transformer means electrically connecting said other current control devices and said control elements, and means for simultaneously applying intermittent electrical energy to the anodes of said evacuated current control devices.

7. The counting circuit as described in claim 6, and including relay means for causing reversal of the order of energization of said principal current control devices.

8. The counting circuit as described in claim 6, and including relay means for connecting said control elements to cause reversal of the order of energizing said principal current control devices.

9. The counting circuit as described in claim 6, the primary windings of said transformer means being in circuit with said intermittent electrical energy means and said evacuated current control devices, and the secondary wind- 10. The counting circuit as described in claim 6, said principal current control devices comprising gaseous electronic tubes.

11. In a counting circuit, a plurality of principal gaseous electronic tubes having grids for control thereof, bias means connected with said grids normally to prevent conduction of appreciable current through said tubes, a plurality of evacuated electronic tubes having grids for control thereof, other bias means connected with the grids of said evacuated tubes normally to prevent conduction of appreciable current therethrough, means electrically connecting said principal electronic tubes with said other bias means and the grids of said evacuated electronic tubes to make possible conduction of appreciable current therethrough as a result of steady current flow through said principal electronic tubes, transformer means electrically connecting said evacuated electronic tubes with the grids and bias means of said principal electronic tubes to cause conduction of appreciable current therethrough as a result of pulsed flow of current through said trans former means and said evacuated electronic tubes, and means for passing intermittent currents through said transformer means and evacuated electronic tubes.

12. The counting circuit as described in claim 11, and including relay means for connecting said transformer means with the grids of said principal electronic tubes to cause reversal of the order of energization of said principal electronic tubes.

13. In a motor control counting circuit, a plurality of motor windings, a plurality of gaseous electronic tubes in circuit therewith, said tubes having control elements therefor, means normally biasing said control elements to prevent substantial flow of current through tubes, a plurality of current control devices having control members therefor, means normally biasing said control members to prevent substantial flow of current through said current control devices, means including means connecting the cathodes of said tubes with said control members to make possible increased flow of current through said current control devices as a result of steady flow of current through said gaseous tubes, transformer means electrically connecting said current control devices and said control elements, and means for applying intermittent electrical energy to said transformer means and said current control devices.

14. The motor control counting circuit as described in claim 13, the primary windings of said transformer means being connected in circuit with said current control devices and said intermittent electrical energy means, and the sec ondary windings of said transformer means being connected in circuit with said control elements and the cathodes of said gaseous electronic tubes.

15. In a counting circuit, a plurality of gaseous grid controlled electronic tubes, a plurality of impedance elements connected in series with said tubes, a plurality of evacuated electronic tubes having grid elements for control of current passing between the anodes and cathodes of said evacuated tubes, a plurality of potential sources connected between said impedance elements and said grid elements and normally biasing said elements sufiiciently negatively to prevent any substantial flow of current through said evacuated tubes, means for providing electrical pulses, said pulse means being connected to said impedance elements and said cathodes, a plurality of transformer primary windings connected in series with said evacuated tubes and in circuit with said electrical pulse means, a plurality of bias devices normally biasing the grids of said gaseous tubes sufficiently negatively to prevent current conduction therethrough, a plurality of transformer secondary windings associated with said primary windings and connected between said bias devices and said impedance elements, and means for quenching said gaseous tubes.

References Cited in the file of this patent UNITED STATES PATENTS Desch et 51 June 3, 1952 Holden Dec. 23, 1952 Nolde Sept. 28, 1954 

